4.80 EDGAR J. ALLEN. 
portion would pass on to the terminal tuft of Th. VIII D, and 
would discharge Th. VII D. In this way the discharge would 
pass right along one side of the thorax, and the particular 
motor fibre concerned would be stimulated in each segment, 
the stimulus being conveyed in its turn to the muscles. If 
we suppose the fibres of the element C to discharge into those 
of D at the point where the fibres cross, the use of this series 
of elements is difficult to understand, as the elements D are by 
themselves capable of discharging each segment. There is, 
however, an alternative supposition. It may be that the 
branches of C influence not either D or E, but some other 
motor element, say F. Then by means of the terminal tufts 
of the D (blue) elements the C (red) elements would all be 
discharged, and they in their turn would stimulate all the F 
elements, which would cause the particular muscle innervated 
by F to discharge. Thus by the stimulation of the element 
D Th. VIII the two muscles innervated by elements E and F 
in each segment, upon one side of the thorax, would be made 
to contract. 
We now pass to the elements A and B, by means of which 
the brain and anterior ganglia are connected with the remain- 
ing ganglia of the cord (elements A, fig. 2), and a particular 
ganglion is put into direct communication with the brain 
(elements B, fig. 3). The fact that the fibres of elements A 
send out collateral branches into the neuropile of each ganglion 
indicates that they control some element which also has 
branches in that particular ganglion, and the suggestion would 
be that by their means a series of elements are stimulated all 
along the body by an impulse from the brain. On the other 
hand, by means of elements B a particular ganglion would be 
placed in more direct communication with the brain. This 
communication will be independent or correlated with a 
stimulus to (or from) all the ganglia through which the fibre 
passes, according to whether the absence of collaterals is the 
true condition of the element, or is due merely to imperfect 
staining. 
With regard to the giant fibres (A (a) Br) a good deal 
